1. Field of the Invention
The present invention relates to a toner cartridge for use in an image forming apparatus such as a laser beam printer or a multi-functional peripheral, particularly to a toner cartridge for containing a toner disposed so as to be exchangeable such as a toner hopper and a toner bottle, and an image forming apparatus using the same.
2. Description of the Related Art
An image forming processing using electrostatic electrophotography is generally composed of respective steps of charging, exposure, developing, transfer, cleaning, charge-removing and fixing. At a step of forming an image, for example, a surface of photoreceptor that is rotationally driven by a charging device is uniformly charged, and the surface of the photoreceptor charged by an exposure device is subjected to irradiation of a laser beam, then an electrostatic latent image is formed. Subsequently, the electrostatic latent image on the photoreceptor is developed by a developing device, and a toner image is formed on the surface of the photoreceptor. The toner image on the photoreceptor is transferred onto a printing paper sheet by a transfer device, then heated by a fixing device, and the toner image is thereby fixed on the printing paper sheet. Further, a residual toner remained on the surface of the photoreceptor after transfer is removed by a cleaning device and collected by a predetermined collecting section, while a residual charge is removed with a charge-removing device from the surface of the photoreceptor after cleaning for preparing for next image formation.
As a developer that develops an electrostatic latent image on a photoreceptor, a one-component developer composed of only a toner or a two-component developer composed of a toner and a carrier is used. The one-component carrier does not need a stirring mechanism and the like for mixing a toner and a carrier uniformly due to no use of a carrier, and thus has an advantage such that a configuration of a developing device is simplified, however, has a disadvantage such that a charging amount of a toner is hardly stabilized due to no use of a carrier, and the like. The two-component developer has a disadvantage in which the stirring mechanism and the like for mixing a toner and a carrier uniformly are required for mixing a toner and a carrier uniformly so that a developing device is complicated, however, is often used for an image forming apparatus for high-speed printing and a color image forming apparatus because of having excellent stability of a charging amount and excellent conformity to high-speed printing.
Recently, in response to a request of a user for low-power consumption and a high quality image, a toner with a small particle size such that a softening temperature is low and a volume average particle size is 5 to 9 μm is often used. Such a toner enables fixing at a low temperature and is effective for high definition and a high quality image including reduction of granularity, however, a toner aggregation is easily generated due to low fluidity of the toner.
Particularly, there is a problem that an external additive of a toner is immersed inside a particle and the fluidity of the toner is thereby extremely lowered due to friction with a sponge-like supply roller that is used as a toner discharge member of a toner cartridge.
To counter this problem, for example, as described in Japanese Unexamined Patent Publication JP-A 2001-83802 and Japanese Unexamined Patent Publication JP-A 2008-216360, by using a screw-type toner discharge member in place of the sponge-like supply roller, it is possible to reduce friction between a supply member and a toner.
However, there is a problem that when the screw-type toner discharge member as described in JP-A 2001-83802 and JP-A 2008-216360 is used, in the case where any vibration is applied to a toner cartridge, a phenomenon such that a toner is unexpectedly flowed out from a cartridge, a so-called toner avalanche, occurs even when the toner discharge member is not in a state of being rotationally driven, not at the time of toner replenishment.
Brief description will be given for the toner avalanche. While the toner discharge member is stopped, a toner in a toner cartridge is in a state where a slope face near a discharge port is kept at an inclination angle that is an approximately repose angle, and when vibration is applied thereto, the entire toner starts to flow so that aerosol in which air and a toner are mixed falls from the discharge port like an avalanche.